The Biology of Polyporus Pargamenus Fries 113 
In decayed wood treated with chlorzinc-iodine the lamellz 
of the prosenchyma elements which remained colorless after 
treatment with hgnin reagents were colored violet. The 
vessel walls, medullary ray cells, and wood parenchyma, 
as well as the middle lamelle of the prosenchyma elements 
assumed a brownish-yellow tint, thus indicating that they 
were still lignified. The tertiary and secondary lay ers of the 
prosenchyma elements which fail to respond to lignin tests 
doubtlessly have been reduced to free cellulose, as evidenced 
by their violet coloration after treatment with chlorzinc- 
iodine. They remain in place until after all the cell-wall 
is delignified but the middle lamella. After all the layers 
of the cell-wall but the primary lamella have become deligni- 
fied the destruction of the cellulose commences. As was seen 
to be the case in the decay of yellow birch wood, these cellu- 
lose layers frequently under go a decided swelling upon the 
appleation of chlorzinc- iodine. The middle lamelle of the 
prosenchyma elements remain in place and respond to tests 
for lignin not only until the tertiary and secondary walls 
have become delignified but even long after they have com- 
pletely disappeared due to the dissolution of the cellulose 
remaining in them. In time, however, even the middle 
lamellee become thinner and thinner until they break up into 
dissociated fragments. Even here microchemical tests show 
that the parts of the middle lamelle which originally formed 
the cell corners, still respond to hgnin tests while the other 
portions respond only to tests for cellulose. 
In the earlier stages of the decay the hyphz tend to extend 
themselves in the direction that offers the least resistance. 
As a result they are found to follow mainly the lumina of 
the various elements, especially those of the vessels. The 
vessel segments, however, are more or less occluded by tylosal 
formations which at first offer some resistance to the spread 
of the hyphe. These tyloses, however, are comparatively 
thin and only serve to retard the spread of the hyphz for a 
time as the fungal hyphe soon dissolve their way through 
and continue their growth. In time the vessels often become 
filled with a dense growth of mycelium. As the decay prog- 
